Broadband communication networks provide a viable alternative to present local exchange carrier (LEC) loops in providing both voice and data transmission services. A variety of broadband network architectures have emerged as supporting Internet and telephony access: including cable distribution networks, ISDN (Integrated Services Digital Network), broadband ISDN, DSL (“Digital Subscriber Line”), ADSL, etc.
A major concern for such broadband communication networks is the need for adequate security measures. The system architecture must ensure user privacy across the network medium and prevent unauthorized access to services. For example, in the case of cable modems based on the Data Over Cable Service Interface Specification (“DOCSIS”, a term referring to the ITU-T J.112 Annex B standard for cable modem systems), security is provided by the DOCSIS Baseline Privacy Interface (“BPI”) which addresses some of the vulnerability presented by the shared cable network. BPI provides security mechanisms, including encryption using the Cipher Block Chaining (CBC) mode of the Data Encryption System (DES) and key exchange based on RSA encryption, that defend against an eavesdropping threat in the cable network. The successor to BPI, DOCSIS 1.1 Baseline Privacy Interface Plus (“BPI+”) adds authentication based on digital certificates that binds media access control addresses for cable modems to RSA public keys. DOCSIS cable modems must be pre-certified with cryptographic keys and/or certificates installed in the hardware at manufacturing time. DOCSIS cable modems undergo a registration process and a baseline privacy key exchange procedure that is used to establish a secure channel with the cable modem termination system (“CMTS”) at the head end. The CMTS verifies a cable modem's public key by verifying the authenticity of the certificate. Use of encryption such as provided by BPI+ is essential for a shared medium access network such as cable.
On the first hop, security measures such as DOCSIS baseline privacy are likely to be adequate. However, the actual path traversed by packets is often complex, and BPI does not provide any data privacy beyond the cable access network. The susceptibility of the public data networks such as the Internet to routing attacks—attacks where the enemy injects false route advertisements possibly to divert traffic to pass an eavesdropping station—is a concern. Quite simply, the science necessary to prevent such attacks does not exist, and it is expected to be a fair number of years before the Internet is adequately protected. In a single, well-managed IP backbone network, it may be possible to take adequate precautions against eavesdropping through good design and rigorous security procedures, though there is still a risk as the equipment and network configuration changes. When traffic traverses more than one backbone (or gets routed over other regional networks of unknown security), however, the potential for attack is greater. In the case of telephony service where ultimate delivery of packets could be via the Internet Protocol to a network not under the control of the service provider, privacy cannot be guaranteed over such paths.
Accordingly, a broadband telephony architecture with enhanced security features is needed, with the overall goals of protecting the privacy of signaling and media traffic and of preventing theft of service.